Expansion device

ABSTRACT

To provide a low-cost expansion device which is capable of changing a passage cross-sectional area of a restriction passage according to the pressure and temperature of introduced refrigerant, without provision of a high-pressure hermetically sealed space. The expansion device comprises a differential pressure valve for having the valve lift thereof controlled according to the differential pressure across the expansion device, and a temperature-sensing section for further controlling the valve lift of the differential pressure valve according to the temperature of refrigerant. The differential pressure valve includes a piston that has a larger outer diameter than that of a valve element and is integrally formed with the valve element. The piston forms a pressure-adjusting chamber into which the inlet pressure of the refrigerant is introduced via a pressure passage, whereby when the inlet pressure of the refrigerant becomes high, the differential pressure valve is caused to operate in a valve opening direction. The temperature-sensing section is formed by filling a bellows that can axially expand and contract, with a wax having a large coefficient of volumetric expansion, whereby the differential pressure valve is caused to operate in a valve closing direction when the inlet temperature of the refrigerant becomes high.

CROSS-REFERENCE TO RELATED APPLICATIONS, IF ANY

This application claims priorities of Japanese Application No.2004-335225 filed on Nov. 19, 2004, entitled “EXPANSION DEVICE”, No.2004-375158 filed on Dec. 27, 2004, entitled “EXPANSION DEVICE”, No.2005-045214 filed on Feb. 22, 2005, entitled “EXPANSION DEVICE” and No.2005-178718 filed on Jun. 20, 2005, entitled “EXPANSION DEVICE”.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to an expansion device used in arefrigeration cycle for an automotive air-conditioner, and moreparticularly to an expansion device which is applicable to arefrigeration cycle using carbon dioxide. (CO₂) and is capable ofefficiently operating the same.

(2) Description of the Related Art

As a refrigeration cycle for an automotive air-conditioner, there isknown not only a refrigeration cycle that employs a receiver forseparating refrigerant condensed by a condenser into a gas and a liquidand a thermostatic expansion valve for expanding liquid refrigerantobtained by the gas/liquid separation but also a refrigeration cyclethat employs an orifice tube for throttling and expanding refrigerantcondensed by a condenser and an accumulator for separating refrigerantevaporated by an evaporator into a gas and a liquid. The orifice tube isformed by a small-diameter tube, and hence it is simple in construction,low in manufacturing costs, and high in the degree of freedom forlayout. However, as is distinct from the refrigeration cycle using thethermostatic expansion valve, the refrigeration cycle using the orificetube causes the refrigerant to be throttled and expanded only by thesmall-diameter tube, and hence is not provided with the function ofcontrolling the flow rate of refrigerant and is incapable of efficientlyoperating the refrigeration cycle in every situation.

In view of this, an expansion device has been proposed which is appliedparticularly to a refrigeration cycle using CO₂ as refrigerant, andconfigured to be capable of changing a restriction passagecross-sectional area of an orifice for throttling refrigerant accordingto the pressure and temperature of refrigerant on a gas cooler outletside, thereby making it possible to efficiently operate therefrigeration cycle (see e.g. Japanese Unexamined Patent Publication(Kokai) No. H09-264622 (FIG. 4)).

This expansion device proposed in Japanese Unexamined Patent Publication(Kokai) No. H09-264622 has a valve structure in which a hermeticallysealed space which is partitioned by a displacement member (diaphragm)is provided on an upstream side of a valve hole, for detecting thepressure and temperature of refrigerant introduced from the gas cooler,and the valve hole is opened and closed by displacement of thedisplacement member from an upstream side. The hermetically sealed spaceis filled with refrigerant at a density within a range ranging from asaturated liquid density at a refrigerant temperature of 0° C. to asaturated liquid density at a critical point of the refrigerant. Thus,when the pressure of the introduced refrigerant is lower than pressurein the hermetically sealed space corresponding to the temperature of therefrigerant, the valve hole is closed, whereas when the pressure of theintroduced refrigerant becomes higher than the pressure in thehermetically sealed space by predetermined pressure, the valve holestarts to open, and when the differential pressure between the pressureof the introduced refrigerant and the pressure in the hermeticallysealed space becomes larger than the predetermined pressure, the valvehole opens at a valve lift dependent on the differential pressure. As aresult, the pressure and temperature of refrigerant on the gas cooleroutlet side can be controlled along an optimum control line determinedby the temperature of the refrigerant on the gas cooler outlet side andpressure maximizing a coefficient of performance, this makes it possibleto efficiently operate the refrigeration cycle using CO₂.

Further, in the case where the refrigerant is CO₂, it is filled in thehermetically sealed space at a liquid density within the above-describedrange, so that when the expansion device is left standing in theatmosphere at normal temperature, the pressure of the refrigerant in thehermetically sealed space becomes very high, causing the differentialpressure between the pressure of the refrigerant in the hermeticallysealed space and the atmospheric pressure to become so large a value ofe.g. 7 to 8 MPa. Therefore, when the expansion device is in the state ofa part not mounted, the displacement member forming the hermeticallysealed space can be deformed or broken due to the large differentialpressure. To cope with this inconvenience, another expansion device hasbeen proposed which has a displacement member configured to be hard tobe deformed or broken (see e.g. Japanese Unexamined Patent Publication(Kokai) No. H11-63740 (FIG. 2)).

In this expansion device proposed in Japanese Unexamined PatentPublication (Kokai) No. H11-63740, a bellows is used as the displacementmember, and while making use of a characteristic of the bellows that ithas durability against external pressure due to its structure, thehermetically sealed space is formed by the bellows and a housingarranged to enclose the bellows from outside, and is filled withrefrigerant. A shaft portion for transmitting the displacement of thebellows to a valve element is inserted into the bellows, and hence evenif high-pressure refrigerant is filled in the hermetically sealed spaceunder an atmospheric pressure environment, the shaft prevents acorrugated portion of the bellows from being deformed inward by thedifferential pressure between the pressure of the refrigerant and theatmospheric pressure.

However, the conventional expansion devices are configured such thatthey include a hermetically sealed space sealed by a displacement memberso as to sense the pressure and temperature of introduced refrigerant tovary the valve lift, and the hermetically sealed space is filled withrefrigerant at very high pressure, and therefore if the expansiondevices are left standing under normal temperature and normal pressureenvironments, there is a danger of rupture of the hermetically sealedspace. This requires a high-level quality control, which increases thecosts of the expansion devices.

SUMMARY OF THE INVENTION

The present invention has been made in view of these problems, and anobject thereof is to provide a low-cost expansion device which dispenseswith a high-pressure hermetically sealed space, and includes arestriction passage which is capable of changing a passagecross-sectional area thereof according to the pressure and temperatureof introduced refrigerant.

To solve the above problem, the present invention provides an expansiondevice for throttling and expanding refrigerant circulating through arefrigeration cycle, comprising a differential pressure valve thatoperates in a valve opening direction as a differential pressure betweena pressure on an upstream side to which the refrigerant is introducedand a pressure on a downstream side from which the refrigerant isdelivered becomes larger, and a temperature-sensing section having ahermetically sealed container that can expand and contract in openingand closing directions of the differential pressure valve, thehermetically sealed container being filled with a solid or liquidmaterial having a large coefficient of volumetric expansion, thetemperature-sensing section causing the differential pressure valve tooperate in a valve closing direction as a temperature of the refrigeranton the upstream side becomes higher.

The above and other objects, features and advantages of the presentinvention will become apparent from the following description when takenin conjunction with the accompanying drawings which illustrate preferredembodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a first embodiment ofthe present invention.

FIG. 2 is a diagram showing the temperature characteristics of atemperature-sensing section.

FIG. 3 is a central longitudinal cross-sectional view showing theexpansion device according to the first embodiment, in an operatingcondition in which the pressure of refrigerant has become high.

FIG. 4 is a central longitudinal cross-sectional view showing theexpansion device according to the first embodiment, in an operatingcondition in which the temperature of refrigerant has become low.

FIG. 5 is a diagram showing the relationship among the differentialpressure across the expansion device according to the first embodiment,the temperature of refrigerant, and the passage cross-sectional area ofa restriction passage.

FIG. 6 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a second embodiment ofthe present invention.

FIG. 7 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a third embodiment ofthe present invention.

FIG. 8 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a fourth embodiment ofthe present invention.

FIG. 9 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a fifth embodiment ofthe present invention.

FIG. 10 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a sixth embodiment ofthe present invention.

FIG. 11 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a seventh embodiment ofthe present invention.

FIG. 12 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to an eighth embodiment ofthe present invention.

FIG. 13 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a ninth embodiment ofthe present invention.

FIG. 14 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a tenth embodiment ofthe present invention.

FIG. 15 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to an eleventh embodimentof the present invention.

FIG. 16 is a system diagram showing a refrigeration cycle to which isapplied the expansion device according to the present invention.

FIG. 17 is a cross-sectional view of essential elements of an expansiondevice according to the present invention which is mounted in aninternal heat exchanger, by way of a first example.

FIG. 18 is a cross-sectional view of essential elements of the expansiondevice according to the present invention which is mounted in aninternal heat exchanger, by way of a second example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described indetail based on an example in which it is applied to a refrigerationcycle using CO₂.

FIG. 1 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a first embodiment ofthe present invention, and FIG. 2 is a diagram showing the temperaturecharacteristics of a temperature-sensing section.

The expansion device according to the first embodiment is disposedwithin a pipe 1 which is laid between a gas cooler and an evaporator ofthe refrigeration cycle, for circulating refrigerant. The expansiondevice includes a differential pressure valve 2 that has a valve liftthereof controlled according to the differential pressure across theexpansion device, and a temperature-sensing section 3 that furthercontrols the valve lift of the differential pressure valve 2 accordingto the inlet temperature of refrigerant. It should be noted that anupper portion of the pipe 1, as viewed in FIG. 1, corresponds to anupstream side into which refrigerant flows from the gas cooler, and alower portion of the pipe 1, as viewed in FIG. 1, corresponds to adownstream side from which refrigerant flows out to the evaporator.

The differential pressure valve 2 has a body 4. A valve hole 5 isaxially formed in an upper central portion of the body 4, and a valveelement 6 in the form of a spool is disposed in the valve hole 5 in amanner movable axially back and forth. When a portion of the valveelement 6, at which the outer diameter of the valve element 6 starts tobe smaller, is located within the valve hole 5, a restriction passagethrough which refrigerant passes has a minimum restriction passagecross-sectional area. The downstream side of the valve hole 5communicates with an outlet port 7 formed in the body 4. The valveelement 6 is integrally formed with a piston 8 extending coaxiallytherewith. The piston 8 has a larger outer diameter than that of thevalve element 6, and is axially slidably disposed within a cylinder 9formed in the body 4. The cylinder 9 has a lower end, as viewed in FIG.1, closed by a lid 10, to thereby form a pressure-adjusting chamber 11.The valve element 6 and the piston 8 are formed with a pressure passage12 axially extending therethrough such that the pressure-adjustingchamber 11 communicates with the upstream side of the differentialpressure valve 2 via the pressure passage 12 so as to introduce theinlet pressure of refrigerant into the pressure-adjusting chamber 11.Further, the pressure-adjusting chamber 11 has a spring 13 disposedtherein for urging the piston 8 toward the upstream side.

The temperature-sensing section 3 is disposed on an upper end of thevalve element 6. The temperature-sensing section 3 comprises a bellows14 that can axially expand and contract, a sealing member 15 that sealsan opening of the bellows 14, and a wax 16 filled in a containerhermetically formed by the bellows 14 and the sealing member 15. Asshown in FIG. 2, the wax 16 has a property that its volume expands witha rise in the temperature. More specifically, the wax 16 has thecharacteristics that when it is in a solid state at a low temperature,or when it is in a liquid state at a high temperature, it has a smallcoefficient of volumetric expansion with respect to the temperature,whereas when it is in a state of solid solution in which it is changedfrom a solid to a liquid, at an intermediate temperature, it has a largecoefficient of volumetric expansion with respect to the temperature.Therefore, the temperature-sensing section 3 forms an actuator whichcontrols the differential pressure valve 2 by sensing temperature withina range in which the wax 16 is in the state of solid solution where thewax 16 has a large coefficient of volumetric expansion. It should benoted that the range of temperatures which the temperature-sensingsection 3 senses is determined by the composition of the wax 16.

Further, the temperature-sensing section 3 is fitted on the upperportion of the valve element 6 by the sealing member 15, and urged by aspring 17 in the direction of closing of the differential pressure valve2. The spring 17 is brought into abutment with a cup-shaped member 18that is mounted on an upper end of the body 4 in a manner such that anupper end of the cup-shaped member 18 covers the temperature-sensingsection 3. The set load of the spring 17 is adjusted by the press-fittedamount of the body 4 press-fitted into an open end of the cup-shapedmember 18. The cup-shaped member 18 has an opening formed in a partthereof, and the opening has a filter 19 provided thereon. It should benoted that the sealing member 15 has a cutout formed in a portionthereof where it is fitted on the valve element 6 such that a spaceaccommodating the temperature-sensing section 3 and the pressure passage12 formed through the valve element 6 and the piston 8 communicate witheach other.

In the expansion device constructed as above, high-temperature,high-pressure refrigerant having flowed out from the gas cooler flowsinto the expansion device from above, as viewed in FIG. 1, through thepipe 1. Then, the refrigerant flows through the expansion device suchthat it flows into the cup-shaped member 18 through the filter 19, andflows out from the outlet port 7 through the restriction passage betweenthe valve hole 5 and the valve element 6 of the differential pressurevalve 2. When passing through the restriction passage, the refrigerantis adiabatically expanded to be changed into low-pressure,low-temperature refrigerant in a gas-liquid two-phase state, andsupplied to the evaporator. In the evaporator, the refrigerant in thegas-liquid two-phase state is evaporated by absorbing heat from airwithin a vehicle compartment, and when evaporated, it cools air in thevehicle compartment by depriving the air of latent heat of vaporization.

Next, a description will be given of the operation of the expansiondevice performed when the pressure and temperature of refrigerantintroduced therein change.

FIG. 3 is a central longitudinal cross-sectional view showing theexpansion device according to the first embodiment, in an operatingcondition in which the pressure of refrigerant has become high. FIG. 4is a central longitudinal cross-sectional view showing the expansiondevice according to the first embodiment, in an operating condition inwhich the temperature of refrigerant has become low. FIG. 5 is a diagramshowing the relationship among the differential pressure across theexpansion device according to the first embodiment, the temperature ofrefrigerant, and the passage cross-sectional area of the restrictionpassage.

First, as shown in FIG. 5, the expansion device has the characteristicsthat in a region where the differential pressure across the expansiondevice is small, the restriction passage has a constant cross-sectionalarea determined by a clearance between the valve hole 5 and the valveelement 6, and that when the differential pressure exceeds apredetermined value, the differential pressure valve 2 starts to open,thereby proportionally increasing the passage cross-sectional area ofthe restriction passage, and at the same time the predetermined value atwhich the differential pressure valve 2 starts to open becomes higher asthe temperature of refrigerant becomes higher. Further, as shown in FIG.2, the wax 16 has a small coefficient of volumetric expansion withrespect to the rise in the temperature when it is in the solid or liquidstate, and it has a very large coefficient of volumetric expansion whenit is in the state of solid solution, so that in FIG. 5, the distancebetween temperature gradients is shown to be small when the wax 16 is inthe solid or liquid state, and larger when the wax 16 is in the state ofsolid solution. In view of the above characteristics, the closed stateof the expansion device, shown in FIG. 1, shows a case in which when thetemperature of refrigerant introduced into the expansion device is e.g.60° C., the differential pressure across the restriction valve is nothigher than 8 MPa, by way of example. At this time, although the valveelement 6 receives the inlet pressure of refrigerant in a valve closingdirection, and the piston 8 receives the inlet pressure introduced intothe pressure-adjusting chamber 11 via the pressure passage 12 in a valveopening direction, a force in the valve opening direction always acts onthe valve element 6 due to the difference in pressure-receiving areabetween the valve element 6 and the piston 8, since the outer diameterof the piston 8 is set to be larger than that of the valve element 6.Therefore, the valve element 6 is stopped at a location where a forcegenerated by the inlet pressure and acting in the valve openingdirection, the load of the spring 17 acting in the valve closingdirection, and the load of the spring 13 interposed in thepressure-adjusting chamber 11 and acting in the valve opening directionare balanced.

After that, from the state shown in FIG. 1, when the inlet pressure ofrefrigerant at the inlet of the expansion device becomes higher with nochange in the inlet temperature of refrigerant, the force in the valveopening direction acting on the valve element 6 due to the difference inpressure-receiving area between the valve element 6 and the piston 8 isincreased, so that the valve element 6 is moved in the valve openingdirection against the urging force of the spring 17 urging the valveelement 6 in the valve closing direction via the temperature-sensingsection 3. When the inlet pressure of refrigerant increases until thedifferential pressure across the restriction passage reaches 8 MPa, thedifferential pressure valve 2 starts to open, and when the differentialpressure exceeds 8 MPa, the passage cross-sectional area of therestriction passage is increased in proportion to the differentialpressure, whereby the expansion device is placed in a state shown inFIG. 3. At this time, since the inlet temperature of refrigerant doesnot change, the wax 16 does not change in volume, and hence thetemperature-sensing section 3 does not expand or contract in the axialdirection.

Further, from the state shown in FIG. 1, when the inlet temperature ofrefrigerant becomes lower with no change in the inlet pressure ofrefrigerant introduced into the expansion device, the volume of the waxcontracts, whereby the temperature-sensing section 3 is axiallyshortened. At this time, since the inlet pressure of refrigerant doesnot change, neither the force acting on the valve element 6 in the valveopening direction due to the difference in pressure-receiving areabetween the valve element 6 and the piston 8, nor the urging force ofthe spring 17 in the valve closing direction changes, so that the valveelement 6 is moved in the valve opening direction by a distancecorresponding to the axial contraction of the temperature-sensingsection 3. As a result, the passage cross-sectional area of therestriction passage becomes larger, whereby the expansion device isplaced in a state shown in FIG. 4.

Of course, in the expansion device, when the inlet pressure ofrefrigerant changes in a decreasing direction, or the inlet temperatureof refrigerant changes in an increasing direction, the restrictionpassage is changed in a direction of decreasing the cross-sectionalarea.

FIG. 6 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a second embodiment ofthe present invention. It should be noted that component elements inFIG. 6 identical to those shown in FIG. 1 are designated by identicalreference numerals, and detailed description thereof is omitted.

The expansion device according to the second embodiment is distinguishedfrom the expansion device according to the first embodiment in that ithas a shorter axial length. More specifically, in the expansion deviceaccording to the first embodiment, the valve element 6, thetemperature-sensing section 3, and the spring 17 are arranged in series,which inevitably increases the axial length of the expansion device. Incontrast, the expansion device according to the second embodiment isconfigured such that the urging force of the spring 17 is transmitted tothe temperature-sensing section 3 via a cup-shaped spring-receivingportion 20. The cup-shaped spring-receiving portion 20 has a flangeportion radially outwardly extending from the open end thereof such thatthe flange portion receives one end of the spring 17, whereby thetemperature-sensing section 3 and the spring 17 are arranged in parallelwith each other while being caused to operate in series, to therebyreduce the axial length of the expansion device, making the expansiondevice compact in size. With this construction, a position where thespring 17 applies the urging force to the temperature-sensing section 3is closer to the valve element 6, and hence the temperature-sensingsection 3 becomes insusceptible to an external force acting in adirection perpendicular to the axis of the expansion device. Thisprevents an upper end of the temperature-sensing section 3, as viewed inFIG. 6, from being swung, whereby the temperature-sensing section 3 canbe stably disposed.

FIG. 7 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a third embodiment ofthe present invention. It should be noted that component elementsappearing in FIG. 7, which have functions identical to or equivalent tothose of the component elements appearing in FIG. 1, are designated byidentical reference numerals, and detailed description thereof isomitted.

The expansion device according to the third embodiment is distinguishedfrom the expansion devices according to the first and second embodimentsin that the construction of the temperature-sensing section 3 ismodified, and the degree of freedom of adjustment of the spring 17 isenhanced. More specifically, in the expansion device, the bellows 14 isdisposed within a cup-shaped member 21, and open ends of the bellows 14and the cup-shaped member 21 are sealed to each other. The wax 16 isfilled between the bellows 14 and the cup-shaped member 21. In theexpansion device, a bottom portion of the cup-shaped member 21 is fittedin a holder 23 rigidly fixed to an upstream-side opening of a hollowcylindrical housing 22 outside the cup-shaped member 21, and the spring17 is interposed between the temperature-sensing section 3 and the valveelement 6. The spring 17 is disposed between a disk 24 disposed on abottom portion of the bellows 14 in contact therewith, and aspring-receiving member 25 having a lower end face, as viewed in FIG. 7,with which the valve element 6 is in abutment. The holder 23 is providedwith an inlet port 26 for introducing refrigerant. The spring-receivingmember 25 has a cutout formed in a portion thereof where thespring-receiving member 25 is brought into abutment with the valveelement 6 such that the space accommodating the temperature-sensingsection 3 communicates with the pressure-adjusting chamber 11 via thepressure passage 12 formed through the valve element 6 and the piston 8.

Further, the expansion device has a bias spring 27 interposed between astepped portion formed on the hollow cylindrical housing 22 and thespring-receiving member 25. The bias spring 27 is configured to bedisposed in parallel with the temperature-sensing section 3 and thespring 17 arranged in series with each other. As described above, thebias spring 27 which does not undergo a change by the temperature isdisposed in parallel with the spring 17 which undergoes a change by thetemperature. This makes it possible to set a combination of the springconstants of the springs 27 and 17, to thereby adjust changes inpressure caused by temperature. It should be noted that the set load ofthe spring 17 and the bias spring 27 is adjusted by the press-fittedamount of the body 4 press-fitted into a lower open end of the hollowcylindrical housing 22, as viewed in FIG. 7.

FIG. 8 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a fourth embodiment ofthe present invention. It should be noted that component elementsappearing in FIG. 8, which have functions identical to or equivalent tothose of the component elements appearing in FIG. 1, are designated byidentical reference numerals, and detailed description thereof isomitted.

The expansion device according to the fourth embodiment is distinguishedfrom the expansion devices according to the first to third embodimentsin that the construction of the temperature-sensing section 3 ismodified. More specifically, the temperature-sensing section 3 of theexpansion device comprises a cup-shaped member 28, a diaphragm 29rigidly fixed to an open flange portion of the cup-shaped member 28, andthe wax 16 filled in a container hermetically sealed by the cup-shapedmember 28 and the diaphragm 29. An upper surface of adisplacement-transmitting member 30 fitted on the valve element 6 is inabutment with a central portion of the diaphragm 29. The spring 17 forurging the temperature-sensing section 3 in the valve closing directionis disposed between the open flange portion of the cup-shaped member 28and the cup-shaped member 18 disposed in a manner covering thetemperature-sensing section 3.

In the expansion device constructed as above, the operation of thedifferential pressure valve 2 responsive to changes in the inletpressure of refrigerant is the same as those of the differentialpressure valves 2 of the expansion devices according to the first tothird embodiments. The wax 16 of the temperature-sensing section 3expands or contracts according to changes in the inlet temperature ofrefrigerant, whereby the central portion of the diaphragm 29 is axiallydisplaced. This displacement is transmitted to the valve element 6 viathe displacement-transmitting member 30 to thereby control the valvelift of the differential pressure valve 2. For example, if thetemperature of refrigerant becomes high, the wax 16 of the cup-shapedmember 28 expands to swell toward the diaphragm 29 displaceable in theaxial direction, which displaces the diaphragm 29 in the valve closingdirection. Inversely, if the temperature of refrigerant lowers, thediaphragm 29 is displaced in the valve opening direction.

FIG. 9 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a fifth embodiment ofthe present invention. It should be noted that component elementsappearing in FIG. 9, which have functions identical to or equivalent tothose of the component elements appearing in FIG. 8, are designated byidentical reference numerals, and detailed description thereof isomitted.

The expansion device according to the fifth embodiment is distinguishedfrom the expansion device according to the fourth embodiment in that theconstruction of the temperature-sensing section 3 is modified. That is,the temperature-sensing section 3 of the expansion device employs acup-shaped member 28 having a hole formed in a bottom thereof, and thecup-shaped member 28 is finally sealed by a ball 31. More specifically,the diaphragm 29 is rigidly fixed to the open flange portion of thecup-shaped member 28 e.g. by laser welding in the atmosphere, and thecup-shaped member 28 is placed in a large container with the bottomformed with the hole positioned upward, and is evacuated. Then, the wax16 liquefied by heating is caused to flow into the cup-shaped member 28through the hole. Further, the ball 31 is placed on the hole of thebottom in a manner closing the hole, and rigidly fixed to the cup-shapedmember 28 e.g. by resistance welding, to thereby hermetically seal thecup-shaped member 28. The wax 16 is thus filled in the cup-shaped member28 of the hermetically sealed container.

In the expansion device constructed as above, the operation of thedifferential pressure valve 2 responsive to changes in the inletpressure of refrigerant is the same as those of the differentialpressure valves 2 of the expansion devices according to the first tofourth embodiments. The wax 16 of the temperature-sensing section 3expands or contracts according to changes in the inlet temperature ofintroduced refrigerant, whereby the central portion of the diaphragm 29is axially displaced. This displacement is transmitted to the valveelement 6 via the displacement-transmitting member 30, to therebycontrol the valve lift of the differential pressure valve 2.

FIG. 10 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a sixth embodiment ofthe present invention. It should be noted that component elementsappearing in FIG. 10, which have functions identical to or equivalent tothose of the component elements appearing in FIG. 9, are designated byidentical reference numerals, and detailed description thereof isomitted.

The expansion device according to the sixth embodiment is distinguishedfrom the FIG. 9 expansion device according to the fifth embodiment inthat the temperature-sensing section 3 and the spring 17 are reverselyarranged. More specifically, in the expansion device, the cup-shapedmember 28 of the temperature-sensing section 3 is fitted in a holeformed in a bottom of the cup-shaped member 18 having the body 4press-fitted in an open lower end thereof, as viewed in FIG. 9, and thespring 17 is disposed between the diaphragm 29 and the valve element 6.As a result, the expansion device is configured similarly to the FIG. 7expansion device according to the third embodiment such that the valveelement 6 is urged in the valve closing direction with respect to thetemperature-sensing section 3 in a fixed positional relationship withthe body 4.

In the expansion device constructed as above, the differential pressurevalve 2 operates in the valve opening direction when the differentialpressure between the inlet pressure and the outlet pressure ofrefrigerant becomes high, and operates in the valve closing directionwhen the inlet temperature of refrigerant introduced into the expansiondevice becomes high, and hence the differential pressure valve 2operates similarly to the differential pressure valves 2 of theexpansion devices according to the first to fifth embodiments.

FIG. 11 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a seventh embodiment ofthe present invention. It should be noted that component elementsappearing in FIG. 11, which have functions identical to or equivalent tothose of the component elements appearing in FIG. 10, are designated byidentical reference numerals, and detailed description thereof isomitted.

The expansion device according to the seventh embodiment isdistinguished from the FIG. 10 expansion device according to the sixthembodiment in that the construction of the differential pressure valve 2is modified. More specifically, the differential pressure valve 2comprises a movable valve seat 32 of which the axial position is changedaccording to the inlet temperature of refrigerant, and a hollowcylindrical valve element 33 of which the valve lift with respect to themovable valve seat 32 is changed by the differential pressure betweenthe inlet pressure and the outlet pressure of refrigerant.

In the temperature-sensing section 3, flange portions fixedly securingthe cup-shaped member 28 and the diaphragm 29 to each other are fixed toan open upper end of the body 4 by swaging, and the movable valve seat32 is pressed against a lower surface of the diaphragm 29 by a spring 34having a large spring force. Thus, the movable valve seat 32 forms avalve seat axially displaced in a manner interlocked with the diaphragm29 axially displaced according to the inlet temperature of theintroduced refrigerant. The hollow cylindrical valve element 33 is heldby the body 4 in a manner movable axially back and forth, and is urgedby a spring 35 in a direction of being seated on the movable valve seat32. The hollow cylindrical valve element 33 is configured such that highinlet pressure acts on an end face opposed to the movable valve seat 32in a direction away from the movable valve seat 32, that is, in thevalve opening direction, and low outlet pressure acts on an end face onan opposite side to the movable valve seat 32 in the valve closingdirection. Therefore, the differential pressure valve 2 is opened andclosed by the differential pressure between the inlet pressure and theoutlet pressure acting on the opposite end faces of the hollowcylindrical valve element 33 and the urging force of the spring 35.

In the expansion device constructed as above, when the differentialpressure between the inlet pressure and the outlet pressure ofrefrigerant is low, and the hollow cylindrical valve element 33 isseated on the movable valve seat 32, thereby closing the differentialpressure valve 2, the minimum flow rate of refrigerant is determined bya clearance between the hollow cylindrical valve element 33 and the body4 holding the valve element 33. Refrigerant introduced from above, asviewed in FIG. 11, is throttled by the clearance, and undergoesadiabatic expansion when flowing out into an downstream-side space wherethe spring 35 is disposed, to be delivered downward, as viewed in FIG.11. At this time, the temperature-sensing section 3 axially expands orcontracts according to the inlet temperature of refrigerant, whereby themovable valve seat 32 is axially displaced, with the differentialpressure valve 2 being closed.

When the differential pressure between the inlet pressure and the outletpressure of refrigerant becomes larger than the urging force of thespring 35, the differential pressure valve 2 is opened. At this time,the valve opening position of the differential pressure valve 2 changesaccording to the inlet temperature of refrigerant detected by thetemperature-sensing section 3. More specifically, when the inlettemperature is low, the movable valve seat 32 is positioned at an upperposition, as viewed in FIG. 11, and when the inlet temperature is high,the movable valve seat 32 is positioned at a lower position, as viewedin FIG. 11. Therefore, as the temperature rises, the movable valve seat32 moves downward, as viewed in FIG. 11, to thereby act in a directionof contracting the spring 35 via the hollow cylindrical valve element33, so that the spring 35 acts to strengthen a spring force thereof. Asa result, the valve opening position of the differential pressure valve2 is shifted toward a higher differential pressure side, and hence thedifferential pressure valve 2 is changed toward a side where it is moredifficult to open the valve 2.

FIG. 12 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to an eighth embodiment ofthe present invention. It should be noted that component elementsappearing in FIG. 12, which have functions identical to or equivalent tothose of the component elements appearing in FIG. 11, are designated byidentical reference numerals, and detailed description thereof isomitted.

The expansion device according to the eighth embodiment is distinguishedfrom the FIG. 11 expansion device according to the seventh embodiment inthat the hollow cylindrical valve element 33 of the differentialpressure valve 2 is provided with a damper mechanism so as to preventthe differential pressure valve 2 from sensitively reacting to a abruptchange in the pressure of introduced refrigerant, to thereby preventhunting of the refrigeration cycle.

The movable valve seat 32 is provided with an orifice 36 for adjustingthe minimum flow rate of refrigerant such that introduced refrigerantcan be caused to flow directly into the inside of the hollow cylindricalvalve element 33 as a space on the downstream side of the hollowcylindrical valve element 33. The hollow cylindrical valve element 33has a groove 37 circumferentially formed in an outer periphery thereofinside a portion of the body 4 that holds the valve element 33. Thegroove 37 communicates with the inside space of the valve element 33 viaa communication hole 38. Therefore, the orifice 36 of the movable valveseat 32, together with the clearance between the valve element 33 andthe body 4 holding the same, determines the minimum flow rate ofrefrigerant capable of being caused to flow in the closed state of thedifferential pressure valve 2.

An annular piston 40, which is axially slidably disposed within acylinder 39 formed in the body 4 on the downstream side of thedifferential pressure valve 2, is fixed to the hollow cylindrical valveelement 33, and the valve element 33 is urged via the piston 40 by thespring 35 in the valve closing direction. The piston 40 defines a damperchamber 41 within the cylinder 39, and the damper chamber 41communicates with the space on the downstream side of the valve element33 via a clearance between the piston 40 and the body 4, and theclearance between the valve element 33 and the body 4 and thecommunication hole 38. Refrigerant flows into and out of the damperchamber 41 through the restricted passages of the clearances, whichserves as a resistance against the axial motion of the piston 40, andforms the damper mechanism of the valve element 33. It should be notedthat the groove 37 and the communication hole 38 formed in the valveelement 33 are for causing high-pressure refrigerant to flow into thelow-pressure downstream side via an intermediate portion of theclearance between the valve element 33 and the body 4 so as to preventhigh-pressure refrigerant from flowing into the damper chamber 41 viathe clearance.

In the expansion device constructed as above, the normal operationthereof is the same as that of the expansion device according to theseventh embodiment shown in FIG. 11. Now, when the inlet pressure ofintroduced refrigerant undergoes a rapid change, although thedifferential pressure valve 2 is about to perform a rapid opening orclosing operation in response thereto, the damper mechanism prevents thehollow cylindrical valve element 33 from performing a rapid opening orclosing operation in a manner following up the rapid opening or closingoperation about to be performed by the differential pressure valve 2. Asa result, when the refrigeration cycle undergoes a rapid change in thepressure of refrigerant, the refrigeration cycle is prevented fromsensitively reacting to the rapid change in the pressure of refrigerantto cause hunting thereof.

FIG. 13 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a ninth embodiment ofthe present invention. It should be noted that component elementsappearing in FIG. 13, which have functions identical to or equivalent tothose of the component elements appearing in FIG. 12, are designated byidentical reference numerals, and detailed description thereof isomitted.

The expansion device according to the ninth embodiment is distinguishedfrom the FIG. 12 expansion device according to the eighth embodiment inthat the construction of the damper mechanism provided for the hollowcylindrical valve element 33 of the differential pressure valve 2 ismodified. More specifically, in the expansion device according to theninth embodiment, the damper chamber 41 is formed by the piston 40 fixedto the valve element 33 and a closing portion 46 fixed to the cylinder39. The closing portion 46 is formed with an orifice 47. Within thedamper chamber 41, the spring 35 is disposed for urging the valveelement 33 in the valve closing direction via the piston 40, and theload of the spring 35 is adjusted by the press-fitted amount of theclosing portion 46 press-fitted into the cylinder 39. A space above thepiston 40, as viewed in FIG. 13, communicates with the space on thedownstream side of the valve element 33 via the communication hole 38formed in the valve element 33, and is always maintained at lowpressure.

In the expansion device constructed as above, the normal operationthereof is the same as that of the expansion device according to theeighth embodiment shown in FIG. 12. Further, when the inlet pressure ofintroduced refrigerant undergoes a rapid change, since the dampermechanism suppresses the rapid opening or closing operation of thehollow cylindrical valve element 33, the differential pressure valve 2is insensitive to the rapid change in the pressure of refrigerant. Thismakes it possible to prevent the differential pressure valve 2 fromsensitively reacting to the rapid change in the pressure of refrigerantto cause hunting of the refrigeration cycle.

FIG. 14 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to a tenth embodiment ofthe present invention. It should be noted that component elementsappearing in FIG. 14, which have functions identical to or equivalent tothose of the component elements appearing in FIG. 11, are designated byidentical reference numerals, and detailed description thereof isomitted.

The expansion device according to the tenth embodiment is distinguishedfrom the FIG. 11 expansion device according to the seventh embodiment inthat the construction of a part of the differential pressure valve 2,where the temperature-sensing section 3 varies the position of the valveseat according to a change in the inlet temperature of refrigerant, ismodified. More specifically, in the expansion device according to theseventh embodiment, the movable valve seat 32 receives low pressure toan area corresponding to the inner diameter of the hollow cylindricalvalve element 33, and hence a large force acts on the movable valve seat32 in a direction of closing the differential pressure valve 2, by thedifferential pressure between the received low pressure and the inletpressure of refrigerant, and this large force is received by the spring34 having a large spring force. In contrast, in the expansion deviceaccording to the tenth embodiment, the valve seat movable by thetemperature-sensing section 3 is configured to be hardly influenced bythe high inlet pressure, whereby the spring 34 is implemented by onehaving a small spring force.

The differential pressure valve 2 comprises a hollow cylindrical movablevalve seat 42 held by the body 4 in a manner movable axially back andforth, and a valve element 43 disposed on the downstream side of themovable valve seat 42. The hollow cylindrical movable valve seat 42 hasan upper end, as viewed in FIG. 14, fitted on thedisplacement-transmitting member 30. Further, the movable valve seat 42has a communication hole 44 formed through a portion thereof toward thedisplacement-transmitting member 30, and is urged by the spring 34toward the temperature-sensing section 3. The valve element 43 iscentered within the cylinder 39 formed in the body 4 on the downstreamside by a plurality of guides 45 extending radially outward from thevalve element 43, and is at the same time axially slidably disposedwithin the cylinder 39, in a state urged by the spring 35 in a directionof being seated on the movable valve seat 42.

The valve element 43 has an end face opposed to the movable valve seat42, which is inwardly recessed in the form of a dish such that thesloped portion of the recessed end face is seated on an outer peripheryof the opposed end face of the movable valve seat 42. This makes itpossible for high-pressure refrigerant to flow into the movable valveseat 42 through the communication hole 44. When the high-pressurerefrigerant flows into the movable valve seat 42, a force acting on themovable valve seat 42 in the downward direction, as viewed in FIG. 14,is cancelled by a force acting on the movable valve seat 42 in theupward direction, as viewed in the figure, since an area having anannular shape corresponding to the radial thickness in cross section ofthe movable valve seat 42 forms a pressure-receiving area on which thehigh pressure acts in the downward direction, and almost all the lowerend face, as viewed in FIG. 14, except for the outer periphery on whichthe valve element 43 is seated, forms a pressure-receiving area on whichthe high pressure acts in the upward direction. Accordingly, the hollowcylindrical movable valve seat 42 forms a movable valve seat which isfree from influence of the high inlet pressure.

In the expansion device constructed as above, the construction in whichthe differential pressure valve 2 performs the opening and closingoperations in response to the differential pressure between the inletpressure and the outlet pressure of refrigerant, and thetemperature-sensing section 3 varies the position of the valve seat ofthe differential pressure valve 2 according to the inlet temperature ofrefrigerant is the same as those of the expansion devices according tothe seventh and eighth embodiments. However, the movable valve seat 42is configured to have a structure for canceling the high pressure, andhence it is possible to reduce the force of the spring 34 urging themovable valve seat 42 toward the diaphragm 29 of the temperature-sensingsection 3.

FIG. 15 is a central longitudinal cross-sectional view of theconstruction of an expansion device according to an eleventh embodimentof the present invention. It should be noted that component elementsappearing in FIG. 15, which have functions identical to or equivalent tothose of the component elements appearing in FIGS. 14 and 13, aredesignated by identical reference numerals, and detailed descriptionthereof is omitted.

The expansion device according to the eleventh embodiment isdistinguished from the FIG. 14 expansion device according to the tenthembodiment in that it has the damper mechanism included in the FIG. 13expansion device according to the ninth embodiment. More specifically,the expansion device includes the piston 40 axially slidably disposed inthe cylinder 39 formed within the body 4 on the downstream side, and theclosing portion 46 for closing the lower end of the cylinder 39, asviewed in FIG. 15, to thereby form the damper chamber 41 therebetween.The piston 40 is integrally formed with the valve element 43, and urgedupward, as viewed in FIG. 15, by the spring 35 disposed between the sameand the closing portion 46. The closing portion 46 is formed with theorifice 47 for adjusting the potency of the damper mechanism incooperation in the clearance between the piston 40 and the cylinder 39.

The expansion device constructed as above has the movable valve seat 42configured to cancel the high pressure, and the valve element 43includes the damper mechanism that reacts insensitively to a rapidchange in the pressure of refrigerant. This makes it possible to reducethe force of the spring 34 urging the hollow cylindrical movable valveseat 42 toward the diaphragm 29 of the temperature-sensing section 3,and prevent hunting of the refrigeration cycle.

By the way, although in the above-described embodiments, the expansiondevices are disposed within the pipe laid between the gas cooler and theevaporator of the refrigeration cycle, for circulating refrigerant, byway of example, this is not limitative, but a refrigeration cycle usingCO₂ as refrigerant, employs an internal heat exchanger to enhanceefficiency thereof, and therefore, actually, each expansion device isdisposed within a pipe laid between the internal heat exchanger and anevaporator, for circulating refrigerant. This causes the expansiondevice to sense the temperature of refrigerant at an outlet of theinternal heat exchanger, for control of high pressure.

Further, it is known that the expansion device as described above sensesthe temperature of refrigerant at an inlet of the internal heatexchanger, and controls high pressure, whereby it is possible to furtherenhance the efficiency of the refrigeration cycle. In the following, adescription will be given of a case where the expansion device accordingto the present invention is applied to the refrigeration cycleconstructed as above.

FIG. 16 is a system diagram showing a refrigeration cycle to which isapplied the expansion device according to the present invention.

The refrigeration cycle comprises a compressor 51 for compressingrefrigerant, a gas cooler 52 for cooling the compressed refrigerant, anexpansion device 53 for throttling and expanding the cooled refrigerant,an evaporator 54 for evaporating the expanded refrigerant, accumulator55 for storing surplus refrigerant in the refrigeration cycle andseparating refrigerant in gaseous phase from the evaporated refrigerantto send the separated refrigerant to the compressor 51. Further, therefrigeration cycle includes an internal heat exchanger 56 forperforming heat exchange between refrigerant flowing from the gas cooler52 to the expansion device 53 and refrigerant flowing from theaccumulator 55 to the compressor 51.

The expansion device 53 is mounted in the internal heat exchanger 56. Indoing this, a temperature-sensing section of the expansion device 53 isdisposed such that it senses the temperature of refrigerant introducedfrom the gas cooler 52 into the internal heat exchanger 56, and adifferential pressure valve is disposed such that high-pressurerefrigerant having passed through the internal heat exchanger 56 isthrottled and expanded to be delivered to the evaporator 54.

FIG. 17 is a cross-sectional view of essential elements of an expansiondevice according to the present invention which is mounted in aninternal heat exchanger, by way of a first example. FIG. 18 is across-sectional view of essential elements of the expansion deviceaccording to the present invention which is mounted in an internal heatexchanger, by way of a second example. It should be noted that in theseexamples, the expansion device in use-has the construction of theexpansion device according to the eighth embodiment shown in FIG. 12.

First, in the first example illustrated in FIG. 17, the internal heatexchanger 56 has a body 57 formed with a refrigerant inlet passage 58into which high-pressure refrigerant is introduced from the gas cooler52. The refrigerant inlet passage 58 communicates with a return passage59 formed to extend through the internal heat exchanger 56 in parallelwith the refrigerant inlet passage 58. The return passage 59 has aterminal end formed with a mounting hole 60 in which the expansiondevice 53 is mounted. The mounting hole 60 is formed to extend throughthe body 57 from the outside thereof to the refrigerant inlet passage 58across the return passage 59, and the expansion device 53 is mounted inthe mounting hole 60 such that the temperature-sensing section thereofis located in the refrigerant inlet passage 58. In the state where theexpansion device 53 is mounted in the mounting hole 60, a pipe 61leading to the evaporator 54 is mounted on the body 57 at an open end ofthe mounting hole 60 in a manner covering the outlet of the differentialpressure valve of the expansion device 53.

When the expansion device 53 is mounted in the mounting hole 60, theupstream side of the differential pressure valve is configured tocommunicate with the return passage 59, and the outer periphery of thebody of the differential pressure valve is sealed by an O ring betweenthe high-pressure upstream side and the low-pressure downstream side ofthe differential pressure valve. An O ring for sealing is also providedon the outer periphery of the body of the differential pressure valvebetween the refrigerant inlet passage 58 and the return passage 59.

The expansion device 53 mounted in the internal heat exchanger asdescribed above directly senses the temperature of refrigerantintroduced from the gas cooler 52 since the temperature-sensing sectionthereof is located in the refrigerant inlet passage 58. Therefore, theexpansion device 53 controls the movable valve seat of the differentialpressure valve according to the inlet temperature of high-pressurerefrigerant, while the differential pressure control valve performsdifferential pressure control of the high-pressure refrigerant. Thisenables the expansion device 53 to control high pressure such that themaximum efficiency is always attained with respect to the inlettemperature of the refrigerant.

Further, according to the second example illustrated in FIG. 18, theexpansion device 53 is mounted such that it is caused to sense thetemperature of refrigerant via a partition wall 62 by making use of thebody 57 of the internal heat exchanger 56 made of a material havingexcellent thermal conductivity. More specifically, the partition wall 62of a chamber accommodating the temperature-sensing section of theexpansion device 53 is integrally formed with the body 57 in a mannerprotruding into the refrigerant inlet passage 58, and at the same timesuch that it has a size suitable for bringing the insertedtemperature-sensing section into intimate contact with the partitionwall 62. This makes it possible to transfer the temperature ofrefrigerant flowing through the refrigerant inlet passage 58 to thepartition wall 62 and further transfer the temperature from thepartition wall 62 to the temperature-sensing section of the expansiondevice 53. In this case, the expansion device 53 can be dispensed withthe O ring for sealing between the refrigerant inlet passage 58 and thereturn passage 59.

Although in the preferred embodiments of the present invention describedheretofore, the temperature-sensing section 3 controls the valve lift ofthe differential pressure valve 2 by making use of changes in thecoefficient of volumetric expansion caused by the temperature of the wax16, this is not limitative, but the temperature-sensing section 3 may beconstructed using a liquid having a large coefficient of volumetricexpansion, such as alcohol, in place of the wax 16. In this case,changes in the coefficient of volumetric expansion with respect tochanges in the temperature of the liquid are linear in a wide range ofchanges in the temperature, so that the distances between temperaturegradients appearing in FIG. 5 are shown to be uniform.

The expansion device according to the present invention is configuredsuch that the differential pressure valve has its valve lift controlledin response to the pressure of introduced refrigerant, and the solid orliquid material contained in the temperature-sensing section and havinga large coefficient of volumetric expansion further controls the valvelift of the differential pressure valve in response to the temperatureof the introduced refrigerant, without provision of any hermeticallysealed container filled with a high-pressure gas. This makes it possibleto enhance safety in handling the expansion device when it ismanufactured, stored, transported, and mounted in the refrigerationcycle.

Further, the expansion device according to the present invention isconfigured such that the differential pressure valve senses the pressureof refrigerant, and the temperature-sensing section senses thetemperature of the refrigerant to thereby vary the cross-sectional areaof a restriction passage, so that it is possible to perform a controloperation similar to those of the conventional expansion devices whichinclude a hermetically sealed space filled with a high-pressure gas tomake them sensitive to the pressure and temperature of refrigerantsimultaneously. This makes it possible to efficiently. operate therefrigeration cycle.

The foregoing is considered as illustrative only of the principles ofthe present invention. Further, since numerous modifications and changeswill readily occur to those skilled in the art, it is not desired tolimit the invention to the exact construction and applications shown anddescribed, and accordingly, all suitable modifications and equivalentsmay be regarded as falling within the scope of the invention in theappended claims and their equivalents.

1. An expansion device for throttling and expanding refrigerantcirculating through a refrigeration cycle, comprising: a differentialpressure valve that operates in a valve opening direction as adifferential pressure between a pressure on an upstream side to whichthe refrigerant is introduced and a pressure on a downstream side fromwhich the refrigerant is delivered becomes larger; and atemperature-sensing section having a hermetically sealed container thatcan expand and contract in opening and closing directions of thedifferential pressure valve, the hermetically sealed container beingfilled with a solid or liquid material having a large coefficient ofvolumetric expansion, the temperature-sensing section causing thedifferential pressure valve to operate in a valve closing direction as atemperature of the refrigerant on the upstream side becomes higher. 2.The expansion device according to claim 1, wherein the hermeticallysealed container includes a bellows having one end thereof closed, and asealing member for hermetically sealing an opening in the other end ofthe bellows.
 3. The expansion device according to claim 1, wherein thehermetically sealed container includes a cup-shaped member, and adiaphragm for hermetically sealing an opening of the cup-shaped member.4. The expansion device according to claim 1, wherein the materialfilled in the hermetically sealed container is a wax.
 5. The expansiondevice according to claim 1, wherein the differential pressure valveincludes a valve element disposed on an upstream side of a valve holesuch that the valve element can be moved forward into or backward fromthe valve hole, a piston having a larger outer diameter than that of thevalve element and at the same time integrally formed with the valveelement on the downstream side of the valve hole, and apressure-adjusting chamber communicated with the upstream side of thevalve hole via a pressure passage formed through the valve element andthe piston, for causing pressure of the introduced refrigerant to act onthe piston in the valve opening direction.
 6. The expansion deviceaccording to claim 5, wherein the valve element of the differentialpressure valve is in the form of a spool, and forms a restrictionpassage having a passage cross-sectional area corresponding to aclearance between the valve element and the valve hole when thedifferential pressure valve is fully closed.
 7. The expansion deviceaccording to claim 5, wherein the temperature-sensing section has afixed positional relationship with respect to a body of the differentialpressure valve, and transmits expansion and contraction of thedifferential pressure valve in opening and closing directions thereof tothe valve element via a spring.
 8. The expansion device according toclaim 1, wherein the temperature-sensing section has a fixed positionalrelationship with respect to a body of the differential pressure valve,the differential pressure valve including a movable valve seat that ischanged in axial position according to an axial displacement thereofcaused by a change in temperature sensed by the temperature-sensingsection, and a hollow cylindrical valve element held by the body in amanner axially movable to and from the movable valve seat, and at thesame time in a state urged in a direction of being seated on the movablevalve seat.
 9. The expansion device according to claim 8, comprisingdamper means for suppressing a rapid motion of the hollow cylindricalvalve element in opening and closing directions thereof.
 10. Theexpansion device according to claim 1, wherein the temperature-sensingsection has a fixed positional relationship with respect to a body ofthe differential pressure valve, the differential pressure valveincluding a hollow cylindrical movable valve seat held by the body in amanner movable axially back and forth such that the hollow cylindricalmovable valve seat is changed in axial position according to an axialdisplacement of the temperature-sensing section caused by a change intemperature sensed by the temperature-sensing section, and configuredsuch that the refrigerant on the upstream side is introduced therein,and a valve element disposed with respect to the hollow cylindricalmovable valve seat on an axially downstream side thereof in a mannermovable to and away therefrom, and at the same time in a state urged ina direction of being seated on the hollow cylindrical movable valveseat.
 11. The expansion device according to claim 10, wherein the valveelement has an end face opposed to the hollow cylindrical movable valveseat, the end face being recessed in the form of a dish such that thevalve element is seated on an outer periphery of an opposed end face ofthe hollow cylindrical movable valve seat.
 12. The expansion deviceaccording to claim 10, comprising damper means for suppressing a rapidmotion in the valve element in opening and closing directions of thevalve element.